Rich, chewy brownies topped with a cloud of chocolate mousse — our chocolate mousse brownies are like something you’d buy in a café, but they’re surprisingly easy to make for a home baker.
How To Make Chocolate Mousse Brownies
Ingredients Needed
For the Brownie Base
- 1 (4 ounce) semisweet chocolate baking bar, chopped
- ¼ cup salted butter
- ⅓ cup vegetable oil
- 1 ½ cups granulated sugar
- 2 eggs, room temperature
- 2 teaspoons pure vanilla extract
- ¾ cup all purpose flour, spooned and leveled
- ½ cup unsweetened dutch processed cocoa powder
- ½ teaspoon baking powder
- ½ teaspoon table salt
For the Chocolate Mousse
- 1 (4 ounces) semisweet chocolate baking bar, chopped
- 1 cup mini marshmallows
- ¼ cup + 1 tablespoon whole milk
- 1 ¼ cup cold heavy cream
- Chocolate syrup for drizzling (optional garnish)
Ingredient Notes
Use room temperature eggs. This helps them blend more easily into the batter and contributes to a better texture.
Ingredient Substitutions
You can use dark chocolate or milk chocolate instead of semisweet chocolate. This will change the sweetness and richness of the mousse.
Ingredient Additions
Add a teaspoon of espresso powder to the brownie layer to give it a more intense chocolate flavor
Fold in one cup of semi-sweet chocolate chips before baking the brownie layer
Tips for Baking The Brownies
When incorporating the dry ingredients into the wet mixture, use a folding motion rather than vigorous stirring to avoid overmixing, which can lead to dense brownies. We don’t recommend using an electric mixer for making the brownie layer.
Start checking your brownies for doneness a few minutes before the recommended baking time. Oven temperatures can vary, and you don’t want to overbake the brownies.
I can’t stress this enough — let the brownie base cool completely before topping it with mousse. If the base is warm, the mousse will slide right off.
Tips for Making The Mousse
We know that mousse cakes can feel intimidating. Instead of traditional mousse made with raw egg, this recipe uses mini marshmallows melted with chocolate and milk. This not only makes it more approachable, but it gives the mousse structure and stability — meaning it’s foolproof.
Cool the chocolate-marshmallow mixture fully before folding in cream. I learned this the hard way in testing: if the chocolate mixture is even slightly warm, it deflates the whipped cream and you end up with a runny mousse. Waiting until it’s room temperature keeps the texture airy and sliceable.
When whipping cream, I stop at soft peaks first. That way, when I add the cooled chocolate mixture, I can beat it to stiff peaks without overwhipping. If you whip to stiff peaks before folding in the chocolate, the mousse can split or turn grainy.
A silicone spatula or an offset spatula makes folding easier without knocking out air. Stirring too aggressively or using a whisk at this stage can undo all the whipping work. In testing, we found a wide spatula made it much easier to lift and turn the mixture without streaks.
Serving Suggestions
The mousse needs at least two hours in the fridge to set properly. I’ve also chilled overnight with no issues — the texture stays light and fluffy. Skipping or shortening this step means the layers won’t hold when sliced.
For those bakery-worthy squares, run your knife under hot water, wipe it clean, and slice. Every cut looks photo-ready.
Garnish Ideas For Your Mousse Brownies
- dusted lightly with extra cocoa powder
- garnish with fresh berries
- make chocolate curls using a baking bar and a thin shaver
- add a dollop of homemade whipped cream
- top with chocolate sauce or caramel sauce or both
Storage Instructions
Store your brownies in an airtight container in the refrigerator. They will stay fresh for up to three days. Keeping them chilled ensures the mousse layer remains firm and the brownies stay moist.
For longer storage, you can freeze the brownies. Place them in a single layer in an airtight container or wrap them tightly in plastic wrap and then aluminum foil. They will last for up to two months in the freezer.
More Brownie Recipes
Chocolate Mousse Brownies
Ingredients
Brownie Base
- 4 ounces semisweet chocolate baking bar, chopped
- ¼ cup salted butter
- ⅓ cup vegetable oil
- 1 ½ cups granulated sugar
- 2 eggs, room temperature
- 2 teaspoons pure vanilla extract
- ¾ cup all purpose flour, spooned and leveled
- ½ cup unsweetened dutch processed cocoa powder
- ½ teaspoon baking powder
- ½ teaspoon table salt
Chocolate Mousse
- 4 ounces semisweet chocolate baking bar, chopped
- 1 cup mini marshmallows
- ¼ cup whole milk
- 1 tablespoon whole milk
- 1 ¼ cup cold heavy cream
- Chocolate syrup for drizzling, optional garnish
Instructions
Brownie Base
- Preheat the oven to 350°F. Line a 9×9 baking pan with parchment, leaving an overhang for easy removal.
- In a medium size microwave safe bowl, melt the chopped semisweet chocolate and butter (microwave in 20 second intervals or over a double boiler). Stir in the vegetable oil until smooth.
- In a large mixing bowl, add the granulated sugar.
- Whisk in the chocolate mixture until fully combined. (The mixture will be thick.)
- Whisk in eggs one at a time until just incorporated. Do not overbeat, you don’t want to add extra air.
- Add the vanilla extract.
- Sift flour, cocoa powder, baking powder and salt over the wet mixture. Gently fold until no dry streaks remain.
- Spread batter evenly in pan. Bake for 22 to 25 minutes, or until the edges are set but the center still looks slightly underbaked.
- Let brownies cool completely in the pan while you make the chocolate mousse.
Chocolate Mousse
- Place the bowl of a stand mixer and wire whip attachment, or a medium size mixing bowl and the tines of a handheld mixer in the freezer.
- In a medium saucepan over low heat, combine the chopped chocolate, mini marshmallows, and milk.
- Stir constantly until the marshmallows and chocolate are fully melted and smooth.
- Let cool to room temperature. This step is important so the heat doesn’t deflate the whipped cream.
- In a large mixing bowl, beat the heavy cream with an electric mixer until soft peaks form.
- Lower the mixer speed to low, and add the cooled chocolate mixture. Increase the mixer speed to high and mix until fully combined and stiff peaks form — do not overwhip.
- Using either a silicone spatula, or an offset spatula, spread the chocolate mousse over the brownies. Cover and chill in the refrigerator for 2 hours.
- Remove the brownies from the refrigerator and slice into 12 equal squares. Garnish with chocolate syrup drizzle if desired. Keep refrigerated until ready to serve.
Notes
- You can substitute regular unsweetened cocoa powder if you are unable to find Dutch processed cocoa. It will result in a lighter brown color of brownie.
- Light brown sugar can be used in place of the granulated sugar for a chewier brownie.
- The brownies can chill in the refrigerator overnight before slicing and serving.
Nutrition
Leave a Comment